An apparatus for the adsorptive cleaning of a gas in general comprises a housing or vessel formed with a support for a body of gas-permeable adsorption agent, e.g. active carbon in a loosely piled state, and with inlet and outlet fittings (ducts) for enabling the gas to be cleaned to be passed through this body of adsorbent in one direction and a regenerating agent, e.g. another gas, to be passed through this body in the opposite direction.
In U.S. Pat. No. 2,083,732, for example, the apparatus for the adsorptive cleaning of gases comprises a pressure-sustaining rigid outer vessel and a thin-wall inner vessel containing the solid adsorption agent. The adsorber is provided with inlet and outlet ducts for gases and is also formed with a heating device which is capable of generating the heat necessary for regenerating of the adsorbent. Between the thin-wall inner vessel and the pressure-sustaining (thick-wall) outer vessel there can be provided layers of insulating material.
The thermal efficiency of such an arrangement is relatively good since it enables the applied heat to be limited only to the body of adsorbent and the thin-wall inner vessel, in producing the high temperature for the regeneration process.
The entire adsorber, with its massive outer vessel and hence high heat capacity, thus need not be heated to the regenerating temperature.
The system has, however, the disadvantage that the rigid connection of the inner vessel at its upper and lower ends, when it is upright or vertically elongated unduly strains the weld joints between the inner and outer vessels and, with repeated stressing and distressing of these joints in the cycling of the adsorber, brings about failure of such connections.
Apart from this, the inner vessel of the conventional system cannot effectively withstand the pressure fluctuations to which it is normally subjected during recycling. For example, the inner vessel is usually subjected to the full pressure of the gas during the process and, because of its thin-wall construction, must be externally supported by the insulating layers.
When this insulation consists of loosely wound turns or a loose-packed particulate material, deformation of the inner vessel is unavoidable.
This problem is also recognized in part in U.S. Pat. No. 2,083,732 and to prevent such distortion of the inner vessel, it is there proposed to provide a gas inlet and outlet duct between the inner and outer vessels with a small opening so that pressure equilibrium can be effected between the pressure within the inner vessel and that in the insulation surrounding it, thereby reducing the net force upon the inner vessel when the latter is operated with pressurized gas.
In recent years, this solution has been found to be ineffective because modern adsorption and regenerating processes operate with rapid build-up and decrease in pressure. As a consequence, these systems have proved to be unsatisfactory and have been avoided of late.